This invention relates to disk shaped recording reproduction devices for reading information from a disk and particularly to mechanisms which prevent vibrations in these devices.
FIG. 3 shows the principal mechanism of a conventional disk shaped recording reproduction device--a compact disk drive. An optical pickup 2, which reads the information on a compact disk 1, is located near the turntable (not shown) which turns when the compact disk 1 is loaded. A clamp 3, which presses against the compact disk 1 and makes it turn together with the turntable, is located above the turntable. The clamp 3 is attached to a free end of a clamp arm 4. The clamp arm 4 is pivoted to a deck base 6 which is supported by four dampers 5 and springs 20.
FIG. 4 is a cross section of the damper 5. A viscous liquid 8 made from a silicon oil which is resistant to viscosity changes and deterioration accompanying temperature changes is sealed within a cylindrical rubber elastic body 7. A protruding rod 9 is placed in the center of the elastic body 7. A disk shaped resistance plate 10 is placed at the lower end of the protruding rod 9.
In the conventional compact disk drive as described above, when the compact disk 1 is loaded onto the turntable, the clamp arm 4 falls and the clamp 3 holds the compact disk 1 against the turntable. Therefore, the motor (not shown) turns the turntable, compact disk 1, and clamp 3 together without the compact disk 1 slipping, and the optical pickup 2 is able to read optically the information on the compact disk 1. Moreover, the damper 5 absorbs the vibrations of the deck base 6 in order to prevent errors as the information on compact disk 1 is read.
In the compact disk configured as described above, the damper 5 is used to prevent vibration while the viscous fluid 8 is a silicon oil which has a small viscosity drop as its temperature increases. However, the good vibration damping characteristics cannot be maintained because the viscosity of the liquid declines with increasing temperature throughout the entire temperature range, for example, from -30.degree. C. to 70.degree. C., to which the viscous fluid is exposed under automobile operating conditions. Moreover, sealing the silicon oil with a thin rubber film makes manufacturing more difficult and increases production costs.